Coco Gauff triumphed over Qinwen Zheng after three sets to become the youngest WTA Finals champion in 20 years. (More Tennis News)
Having fallen behind in Saturday's final in Riyadh, Gauff bounced back to prevail 3-6 6-4 7-6 (7-2).
Gauff had squandered two match points when 6-5, 40-15 up in the decider, with Zheng clawing back to force a tie-break.
Yet, the American rediscovered her composure to cruise into a 5-0 lead, and though she saw another two match points fall by the wayside, Gauff got the job done at the fifth time of asking.
A short Zheng return clipped the top of the net, with Gauff scrambling from the baseline to meet it before flicking a forehand to the left of her opponent, with this year's Olympic champion unable to get there.
Gauff, who beat Iga Swiatek in the group stage and downed world number one Aryna Sabalenka in the semi-finals, collapsed to the court in celebration, after winning what was the second-longest WTA Tour-level final of 2024.
Data Debrief: It's a marathon, not a sprint
Zheng made a blistering start, but despite going a break up in the second set, she could not maintain the momentum.
Gauff's wobble in the decider meant the WTA Finals championship match had to be decided by a third-set tie-break for the first time since the tournament's introduction in 1972.
At 20, Gauff is the youngest player to win the WTA Finals since Maria Sharapova in 2004, and the youngest American champion of the event since Serena Williams in 2001.
Only Nancy Richey and Anna Smashnova (10 each) have won more titles after their first 10 WTA Tour-level finals than Gauff (nine) in the Open Era.
Meanwhile, she is the first player since Williams (12, between the 2013 US Open and 2015 Cincinnati Open) to win at least eight consecutive hard-court finals, and the youngest to do so since Martina Hingis in 1998.
